DESCRIPTION OF THE PHYLUM PRIAPULA (THEEL 1906)
| EUKARYA> UNIKONTA> OPISTHOKONTA> ANIMALIA> BILATERIA> PROTOSTOMATA> ECDYSOZOA> SCALIDOPHORA> PRIAPULA |
PHYLUM PRIAPULA LINKS
| Priapula (pri-AP-u-la) is formed from the name for the Greek god of fertility, Priapos (Πριαποσ; Latinized to Priapus). The reference is to the penis-like appearance of the animal. |
| INTRODUCTION TO PRIAPULA The priapulids are worm-like animals with an anterior feeding cone (the introvert) that has characteristic hooked spines on it (Figure 1). Figure 2 illustrates the complete digestive tract and large body cavity. They have erythrocytes and amoeboid cells in the fluid of the body cavity. In addition, priapulids have a distinctive larva that has a lorica, which is shed in its transformation to an adult. The priapulids are burrowing animals and the largest of the non-arthropod ecdysozoans. They have a long fossil record that goes back to the time of the Burgess shale, early to mid-Cambrian (Figure 3). Nielsen (2001) suggests that the priapulids were some of the dominant predators in the Cambrian seas. Priapulids belong to a clade of ecdysozoans called Scalidophora (Schmidt-Rhaesa 1998, Nielsen 2001, and Telford et al. 2008, Figure 4), which includes the kinorhynchs. It likely also includes the Loricifera, but little work has been done on them to warrant anything but a provisional connection. Morphological synapomorphies of the clade include an introvert with similar musculature and scalids, small spine like structures on the cuticle of the introvert (Schmidt-Rhaesa 1998, and Nielsen 2001). The two classes of the priapulids feed differently. Animals of the Seticoronaria are small (< 3mm) and resemble Kinorhyncha, but their scalids form tentacles that create a feeding trap (Brusca and Brusca (2003). Priapulida are relatively large animals (5-150 mm) and they are active predators. |
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| FIGURE 1. Photograph of a living priapulid. Image from http://classes.seattleu.edu/biology/biol235/hodin/nematodePriapulidGroup/priapulid/basics.htm | FIGURE 2. A diagram of the internal anatomy of a priapulid. It illustrates the complete digestive tract and large body cavity. Image from http://biodidac.bio.uottawa.ca/ | FIGURE 3. Fossil of Ottia, a priapulid that lived in the Burgess Shale animal community. Top image is a reconstruction. Image from http://www.nmnh.si.edu/paleo/shale/pottoia.htm |
FIGURE 4. The Priapulida (classes within the shaded box) and its position within the Scalidophora (clade S).
P = Protostomata
S = Scalidophora
N = Nematoida
PA = Panarthropoda
| LITERATURE CITED Barnes, R. D. 1980. Invertebrate Zoology. Saunders College/Holt, Rinehart and Wilson, Philadelphia. Barnes. R. S. K. 1984a. Kingdom Animalia. IN: R. S. K. Barnes, ed. A Synoptic Classification of Living Organisms. Sinauer Associates, Inc., Sunderland, MA. pp. 129-257. Brusca, R. C. and G. J. Brusca. 2003. Invertebrates. Sinauer Associates, Inc. Sunderland, Mass. Buchsbaum, R. 1938. Animals Without Backbones, An Introduction to the Invertebrates. The University of Chicago Press. Chicago. Hickman, C. P. 1973. Biology of the Invertebrates. The C. V. Mosby Company. Saint Louis. Margulis, L. and K. Schwartz. 1998. Five kingdoms, an illustrated guide to the phyla of life on earth. 3rd Edition. W. H. Freeman and Company. New York. Nicholas, W.L. 2001b. The pseudocoelomate Ecdysozoa. In: Anderson, D.T., ed. Invertebrate Zoology. Oxford University Press. Oxford, UK. pp. 98-119. Nielsen, C. 2001. Animal Evolution: Interrelationships of the Living Phyla. 2nd Edition. Oxford University Press. Oxford. Pechenik, J. A. 2005. Biology of the Invertebrates. McGraw-Hill. New York. Schmidt-Rhaesa, A. 1998. Phylogenetic relationships of the Nematomorpha – a discussion of current hypotheses. Zoologischer Anzeiger 236:203-216. Storer, T. I. and R. L. Usinger. 1965. General Zoology. 4th Edition. McGraw-Hill Book Company. New York. Telford, M. J. S. J. Bourlat, A. Economou, D. Papillion, and O. Rota-Stabelli. 2008. The evolution of Ecdysozoa. Phil. Trans. R. Soc. B. 363: 1529-1537. Theel, H. 1906. Northern arctic invertebrates in the collections of the Swedish State Museum II. Priapulids, Echiurids, etc. K. Svenska Vetensk. Akad. Handl. 40(4) Tudge, C. 2000. The Variety of Life, A Survey and a Celebration of all the Creatures That Have Ever Lived. Oxford University Press. New York. |
| By Jack R. Holt and Carlos A. Iudica. Last revised: 04/10/2013 |
